[newlib-cygwin] yield: Don't lower thread priority, it leads to starvation
Corinna Vinschen
corinna@sourceware.org
Wed Mar 8 16:44:00 GMT 2017
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=51a993c266581ba41f1622abd274d9848a37cf1d
commit 51a993c266581ba41f1622abd274d9848a37cf1d
Author: Corinna Vinschen <corinna@vinschen.de>
Date: Wed Mar 8 17:44:15 2017 +0100
yield: Don't lower thread priority, it leads to starvation
...and it's not required anymore to have the same effect as the original
code post-XP.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Diff:
---
winsup/cygwin/miscfuncs.cc | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/winsup/cygwin/miscfuncs.cc b/winsup/cygwin/miscfuncs.cc
index 2117eb9..e2ab7a0 100644
--- a/winsup/cygwin/miscfuncs.cc
+++ b/winsup/cygwin/miscfuncs.cc
@@ -85,17 +85,18 @@ check_iovec (const struct iovec *iov, int iovcnt, bool forwrite)
void
yield ()
{
- int prio = GetThreadPriority (GetCurrentThread ());
- SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_IDLE);
- /* MSDN implies that SleepEx will force scheduling of other threads.
+ /* MSDN implies that Sleep will force scheduling of other threads.
Unlike SwitchToThread() the documentation does not mention other
cpus so, presumably (hah!), this + using a lower priority will
stall this thread temporarily and cause another to run.
(stackoverflow and others seem to confirm that setting this thread
to a lower priority and calling Sleep with a 0 paramenter will
- have this desired effect) */
+ have this desired effect)
+
+ CV 2017-03-08: Drop lowering the priority. It leads to potential
+ starvation and it should not be necessary anymore
+ since Server 2003. See the MSDN Sleep man page. */
Sleep (0L);
- SetThreadPriority (GetCurrentThread (), prio);
}
/* Get a default value for the nice factor. When changing these values,
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